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Varied Human Influences on Estuaries, San Francisco Bay, California

Scientists collecting biological samples from mud flats near Hunters Point, California.
Scientists collecting biological samples from mud flats near Hunters Point, a Superfund site in San Francisco Bay, California. The samples provided data for a tool that can help assess the effectiveness of the remediation of contaminated sediments. Photo credit: Richard Luthy, Stanford University.

A photo collage of Hunters Point, a Superfund site in San Francisco Bay, California.
Hunters Point, a Superfund site in San Francisco Bay, California, that's heavily contaminated with polychlorinated biphenyls (PCBs), was used as a study area to develop tools and methods to assess contaminated sediments. The standard method to assess an ecological hazard made analyses very difficult and inconclusive. Therefore, the goal of USGS scientists and their colleagues was to characterize the relationship between bioavailable PCB (controlled in situ by amendments of activated carbon) and the functional ecology of the benthic community.

A bar graph that shows the months that peak chlorophyll concentrations occurred.
Phytoplankton populations in estuaries such as San Francisco Bay, California, are influenced by a host of local stresses that mask plankton responses to global climate change. The above bar graph shows the months that peak chlorophyll concentrations occurred in 116 coastal water bodies in the northern temperate zone. The distribution is surprisingly even from March through September, although, peaks occurred throughout the year. The distribution shows no characteristic single seasonal pattern, a large departure from the regular seasonal pattern of plants on land that is tightly tied to the annual climate cycle (The graph is a modified version of figure 4 from Cloern and Jassby, 2008).

USGS scientists picking clams out of San Francisco Bay bottom sediments in box sieves.
USGS scientists picking clams out of San Francisco Bay bottom sediments in box sieves on board the USGS Research Vessel Polaris.

This set of graphs shows the data used to document the changes in San Francisco Bay phytoplankton.
This set of graphs summarize the data used to document the changes in San Francisco Bay phytoplankton (as measured by chlorophyll a concentrations) caused by the decrease in ocean temperature.

A scientist preparing a submersible instrument package that is used to collect water-quality data.
USGS scientist preparing a submersible instrument package that is used to collect water-quality data on the San Francisco Bay, Calif., during a cruise of the USGS Research Vessel Polaris. The instrument includes sensors for measuring depth, conductivity, temperature, suspended solids, chlorophyll, light penetration, and dissolved oxygen.

Diagram of 3 scenarios of potential selenium discharges and bioaccumulation.
Three scenarios of potential selenium discharges and bioaccumulation that could result from a proposed extension of the San Luis Drain, California. The DYMBAM model was used as part of a larger model to develop the scenarios of effects in the San Francisco Bay, California (figure taken from USGS Fact Sheet 2004-3091).

Microscopic views of typical phytoplankton.
Microscopic views of typical phytoplankton.

The invasive Asian clam, Corbula amurensis.
The invasive Asian clam, Corbula amurensis, has changed the food web in San Francisco Bay estuary by severely restricting phytoplankton blooms in the northern embayment.

Slide about phytoplankton and invasive phytoplankton feeders.
One-celled plants, such as phytoplankton, are the base of the food web in San Francisco Bay. The ability to predict phytoplankton growth is key to assessing the impacts of invasive phytoplankton feeders, such as the Asain Clam, on San Francisco Bay's ecosystem.

View of the Sacramento River, California, at sunrise
Sacramento River, California, is the largest tributary in the San Francisco Bay watershed. USGS scientists have studied the transport of pesticides in the river to gain insight on the fate of pesticides in San Francisco Bay.

Scientist collecting water samples for analysis for pesticide content in the San Joaquin River.
USGS scientist collecting water samples for analysis for pesticide content in the San Joaquin River. The sampling was part of a study to determine the transport and fate of pesticides in San Francisco Bay, Delta, and watershed, California.

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Page Last Modified: Thursday, 01-Aug-2013 12:20:35 EDT